LMTV M1078 Wont start.

[Ronmar]

What Geo said, the transfer case and trans use same oil so if trans oil is
o k, somis the trans case.

the oil light in the dash is driven by the 15 PSI oil pressure switch which is located by the oil pressure gauge sender down on the left side of the engine block. if the light isn’t going out, the alternator also isn’t coming online as alt excitation is controlled by that oil pressure light circuit...

 

[Issati]

What Geo said, the transfer case and trans use same oil so if trans oil is
o k, somis the trans case.

the oil light in the dash is driven by the 15 PSI oil pressure switch which is located by the oil pressure gauge sender down on the left side of the engine block. if the light isn’t going out, the alternator also isn’t coming online as alt excitation is controlled by that oil pressure light circuit...

So what do you suggest I do??

 

[Ronmar]

So what do you suggest I do??

Do you have oil pressure above 15 PSI on the gauge? If so you probably have a bad/shorted oil pressure switch...

 

[Issati]

Do you have oil pressure above 15 PSI on the gauge? If so you probably have a bad/shorted oil pressure switch...

I have 40PSI for oil.
The one weird thing that I've noticed is, when transmission controller is plugged in my rear tire pressure shoots up to over120, you know what the car is turn off and it stays there as if it's not working at all correctly. But when unplug transmission controller, the tire pressure is shown correctly but I lose my NN.
Can all of these problems be related? Can it be that my transmission controller not working correctly and so not letting the car start and showing the wrong tire pressure and lowoil light stays on?

 

[Ronmar]

I have 40PSI for oil.
The one weird thing that I've noticed is, when transmission controller is plugged in my rear tire pressure shoots up to over120, you know what the car is turn off and it stays there as if it's not working at all correctly. But when unplug transmission controller, the tire pressure is shown correctly but I lose my NN.
Can all of these problems be related? Can it be that my transmission controller not working correctly and so not letting the car start and showing the wrong tire pressure and lowoil light stays on?

one weird thing? You got all kinds of weird things going on.

the air gauges on the left are brake pressure. The rear is main and the front is secondary brake system pressure. All the gauges get fed 24V from CB77. In the case of the air brake gauges, the 24v passthru them down to the air brake pressure sensors right under the left dash, the pressure sensors give a varying resistance to ground as the pressure changes.. sounds like something is interfering with that path either thru a short circuit or by adding something into a circuit that does not belong there.

with the dash panel unbolted and lifted, I would look over all the connections and the cables going to-from those gauges and the trans controller. I would also remove the trans controller from the dash, then remove it’s case so you can see the circuit boards. There have been some instances of water intrusion filling the bottom of that case and causing short circuits and board damage...

the oil light circuit is a lot farther removed from the trans and gauges so that is probably an unrelated issue. A quick test for a bad switch would be to unplug it at the switch down alongside the block and put in a jumper across the pins on the truck side connector, then turn on the main switch and see if the oil light goes out...

you weren’t trying to start the truck with the trans controller unplugged were you? It needs to be plugged in and powered to give you that neutral start relay contact over in the VIM that powers the K1 start relay...

 

[Issati]

I finally got to drive it!!!!!!
I wanted to take a moment to thank all of you especially @Ronmar for helping me get this far.

I opened the 3 Valves of CTIS pressure control unit and the smaller one had dirt and mud stuck in there. Cleaned it up and put it all back together and the jiggling part that I posted in previous video (the deflate pressure regulator/relief valve) is no longer jiggling. This did not fix the breaks issue. the tanks did not pass 90PSI. It seems like the air is being dumped out of the system under the passenger side, outside of the cabin.

So then I removed the entire CTIS system and capped the valves that is feeding the system with air. This caused the pressure to reach 120, the beeping stopped and the air breaks started working correctly. I drove the truck and everything seemed to be working correctly.
I still had that Oil pressure light and the Stop light on but the truck worked correctly. I was able to get it up to the 6th gear on a dirt road.


I opened the CTIS pressure control unit thinking I might be able to fix it but there is not much going on in here.





Tomorrow ill work on the oil pressure light. It is showing a 60PSI for oil pressure but the light stays on.
I also noticed that the engine temperature gauge is not working and stay son zero.


Merry Christmas everyone. Wishing you a great day.

 

[Ronmar]

I finally got to drive it!!!!!!
I wanted to take a moment to thank all of you especially @Ronmar for helping me get this far.

I opened the 3 Valves of CTIS pressure control unit and the smaller one had dirt and mud stuck in there. Cleaned it up and put it all back together and the jiggling part that I posted in previous video (the deflate pressure regulator/relief valve) is no longer jiggling. This did not fix the breaks issue. the tanks did not pass 90PSI. It seems like the air is being dumped out of the system under the passenger side, outside of the cabin.

So then I removed the entire CTIS system and capped the valves that is feeding the system with air. This caused the pressure to reach 120, the beeping stopped and the air breaks started working correctly. I drove the truck and everything seemed to be working correctly.
I still had that Oil pressure light and the Stop light on but the truck worked correctly. I was able to get it up to the 6th gear on a dirt road.


I opened the CTIS pressure control unit thinking I might be able to fix it but there is not much going on in here.

View attachment 821749



Tomorrow ill work on the oil pressure light. It is showing a 60PSI for oil pressure but the light stays on.
I also noticed that the engine temperature gauge is not working and stay son zero.


Merry Christmas everyone. Wishing you a great day.

On a A0 with a 3116 Engine, not warming up is not unusual. They diverted all the bypass coolant down to the transmission cooler, so you have to warm up the transmission before the engine can warm up...

 

[Issati]

On a A0 with a 3116 Engine, not warming up is not unusual. They diverted all the bypass coolant down to the transmission cooler, so you have to warm up the transmission before the engine can warm up...

Any ideas about what's wrong with the CTIS pressure control unit? should I buy a new one?

 

[Ronmar]

Your valve looks good, it may still be leaking though. You need to put pressure in on it’s inlet, cap the outlet then close the control solenoid and see if it is leaking Anywhere. If you are hearing air under the truck, You also need to feed air down toward the rest of the CTIS system and find where it is leaking. Hook up a compressor and give it 50-60 PSI and look for the leaks

 

[Coffey1]

Ohm the coils to see if they are all good.

 

[tennmogger]

On a A0 with a 3116 Engine, not warming up is not unusual. They diverted all the bypass coolant down to the transmission cooler, so you have to warm up the transmission before the engine can warm up...

Ron, there may have been an attempt to correct that cooling issue. Two LMTVs I have had apart had a machined restrictor in the left side inlet of the tranny cooler. Can't remember for sure but remaining passage is half an inch or so.

 

[Ronmar]

Ron, there may have been an attempt to correct that cooling issue. Two LMTVs I have had apart had a machined restrictor in the left side inlet of the tranny cooler. Can't remember for sure but remaining passage is half an inch or so.

They actually show that restrictor in the 24P manual. Even in place it will still move more heat than the engine can make down to the cooler and out to the trans. They did actually completely fix this issue... They did away with that bypass pipe entirely on the A1 and A1R and left the engine plummed as cat originally designed it...

 

[coachgeo]

They actually show that restrictor in the 24P manual. Even in place it will still move more heat than the engine can make down to the cooler and out to the trans. They did actually completely fix this issue... They did away with that bypass pipe entirely on the A1 and A1R and left the engine plummed as cat originally designed it...

with that in mind....... would it behove one to at some point get the necessary parts to convert their A0 over to a more typical trans. cooler and a CAT thermostat housing and plumbing?

 

[Issati]

Does anyone know where these go?


TL501 and TL502 cables. They are on the passenger side

 

[Ronmar]

with that in mind....... would it behove one to at some point get the necessary parts to convert their A0 over to a more typical trans. cooler and a CAT thermostat housing and plumbing?

I think it would, the engine will be happier being able to reach and maintain its designed operating temp reliably. I am going to do it when I install my block heater.

You don’t need another thermostat housing. It appears they extended the casting on the normal one into an elbow, so you simply need to cut the elbow off. It may require a new water pump though as they shortened that port to accommodate the elbow on the thermostat housing and installed a freeze plug for the LMTV water pump, so there is only room for a single hose clamp on that water pump port after the freeze plug is removed... and of course the 5th port on the trans cooler will need to be plugged, and a new home for the ether temp switch will need to be found...

Reverting to the normal bypass pathway also removes the need for a LMTV specific water pump and you can source a standard 3116 water pump thru just about any auto parts supplier.

 

[Ronmar]

Does anyone know where these go? View attachment 821790View attachment 821791


TL501 and TL502 cables. They are on the passenger side

Thats a good one. The TL list in the A0 schematic ends at TL320... the A1 does have TL’s up into the 500’s, but I have only noticed them on the schematics I have, and have not seen a 501 or 502 specifically... things that make you go Hmmm... You may have to trace them by hand...

 

[Issati]

So I spend the entire day trying to see how to start this from the inside.
This is what I figured out. when master switch is on, the red start engine button has about 0.7-0.85Volts going through it. Not sure what it is suppose to be.

So here is what I think is happening.
The oil pressure sensor is not working correctly and thus not allowing the engine to start. When I manually start the car, it starts and works correctly however the Oil light and the STOP light stay on. The car thinks that there is something wrong with the oil. (all oils have been filled correctly.)
I think if i change the oil sensors my problems will be resolved. (When I drive the car it shows 60PSI oil)
What do you guys think.

Also see the picture bellow, It seems like some one had messed around with the sensor, I took the electrical tape off the wires here.

 

[Ronmar]

So I spend the entire day trying to see how to start this from the inside.
This is what I figured out. when master switch is on, the red start engine button has about 0.7-0.85Volts going through it. Not sure what it is suppose to be.

So here is what I think is happening.
The oil pressure sensor is not working correctly and thus not allowing the engine to start. When I manually start the car, it starts and works correctly however the Oil light and the STOP light stay on. The car thinks that there is something wrong with the oil. (all oils have been filled correctly.)
I think if i change the oil sensors my problems will be resolved. (When I drive the car it shows 60PSI oil)
What do you guys think.

Also see the picture bellow, It seems like some one had messed around with the sensor, I took the electrical tape off the wires here.

View attachment 821866

No, the oil pressure switch won’t keep it from starting unless it is open(the condition it is supposed to be in when it goes above 15PSI), in which case neither the oil nor stop light would be lit. It being shorted when the engine is not above 15 PSI provides a path to ground to energize those lights and K11(alt excite) and K24(start lockout) relays.

Once the engine starts, and the oil switch goes over 15PSI, those lights and relays de-energize. The alt excite relay de-energizing turns on the alternator, and the start lockout de-energizing removes the path to the start button, so it can no longer crank the starter if the engine is running and above 15PSI of oil pressure.

we already determined earlier in this discussion that you were not getting 24v thru the neutral start contacts of the VIM to relay K1... thats why K1 won’t energize when you complete the path to ground with the start button and lockout relay and why it won’t start from inside the cab. On the VIM connector PX33 you should have DC voltage measured to ground on pins B1, C1, F1 J1 and J2... Do you have all those?

looks like that oil pressure switch connector went bad and someone spliced it together by hand... if the switch was OK, it should still work like that.

 

[Issati]

No, the oil pressure switch won’t keep it from starting unless it is open(the condition it is supposed to be in when it goes above 15PSI), in which case neither the oil nor stop light would be lit. It being shorted when the engine is not above 15 PSI provides a path to ground to energize those lights and K11(alt excite) and K24(start lockout) relays.
Once the engine starts, and the oil switch goes over 15PSI, those lights and relays de-energize. The alt excite relay de-energizing turns on the alternator, and the start lockout de-energizing removes the path to the start button, so it can no longer crank the starter if the engine is running and above 15PSI of oil pressure.

we already determined earlier in this discussion that you were not getting 24v thru the neutral start contacts of the VIM to relay K1... thats why K1 won’t energize when you complete the path to ground with the start button and lockout relay and why it won’t start from inside the cab. On the VIM connector PX33 you should have DC voltage measured to ground on pins B1, C1, F1 J1 and J2... Do you have all those?

looks like that oil pressure switch connector went bad and someone spliced it together by hand... if the switch was OK, it should still work like that.

Okay boys we did it.
It now starts right up. As Ronmar said the problem was from the VIM control. I had 6 relays in there 5 of which were 24 volt and one that was 12 volt.
when I changed that to a 24 volt the problem was resolved.



I want to take this opportunity to thank everyone for helping me with this.


The only problem that I have to fix now is the oil pressure lite that stays on after starting it.

 

[Ronmar]

Okay boys we did it.
It now starts right up. As Ronmar said the problem was from the VIM control. I had 6 relays in there 5 of which were 24 volt and one that was 12 volt.
when I changed that to a 24 volt the problem was resolved.

View attachment 823015

I want to take this opportunity to thank everyone for helping me with this.


The only problem that I have to fix now is the oil pressure lite that stays on after starting it.

No, you just had a bad NS relay. Two of the relays(NS and SF-03) are supposed to be 12V, so you need to get a pair of 12V relays from your local auto parts store and replace them. The reason why this is important is that the dropout voltage on a 24V relay is not very far below the normal 12V voltage.

A 24V relay in the NS position may not reliably stay energized while you are trying to crank the engine...